JP5793332B2 - Nonaqueous electrolyte battery separator and lithium ion secondary battery - Google Patents

Description

  The present invention relates to a separator for a non-aqueous electrolyte battery and a lithium ion secondary battery using the separator.

  Conventionally, a porous membrane made of polyolefin having fine pores has been used as a separator of a lithium ion secondary battery. In a lithium ion secondary battery equipped with this separator, if abnormal heat is generated due to overcharging, short circuit inside or outside the battery, etc., the separator melts when it reaches a high temperature (140 to 160 ° C.), and the micropores are closed to conduct ions. The current is cut off by suppressing (referred to as shutdown). In OA equipment, home appliances, communication equipment, etc., where small and small-capacity lithium-ion secondary batteries are used, by adding this shutdown function to the separator, the expansion of the effect of short-circuiting is suppressed, and electrolytes are decomposed. Smoke and fire (thermal runaway) could be prevented.

  On the other hand, in lithium ion secondary batteries having large capacity and high energy density used in electric vehicles (HEV, EV), uninterruptible power supplies, load conditioners, etc., the temperature of the battery cell is changed from the polyolefin porous membrane due to abnormal heat generation. The case where it exceeds 140-160 degreeC which is the shutdown temperature of the separator which becomes will be assumed. When the temperature of the battery cell exceeds the shutdown temperature of the separator, the separator contracts and the pores expand, and then completely melts by heat. There was a possibility of being connected to. Therefore, it has been desired to improve the heat resistance of the separator.

  As a separator with improved heat resistance, it contains a porous sheet-like substrate (resin film, woven fabric / nonwoven fabric, paper, etc.) made of a heat-resistant thermoplastic material, and heat-resistant fine particles such as inorganic fine particles. Various separators have been proposed.

  Patent Document 1 discloses a separator for a non-aqueous electrolyte battery including a substrate such as a nonwoven fabric, a heat-resistant nitrogen-containing aromatic polymer, and a ceramic powder. A heat-resistant nitrogen-containing aromatic polymer such as an aromatic polyamide acts as a binder between the ceramic powder and the substrate. Although the heat resistance is improved as compared with polyolefin and the like, since the binder is a thermoplastic resin, the separator described in Patent Document 1 is a lithium ion secondary battery that requires high energy density. It was difficult to say that the separator of the secondary battery had sufficient heat resistance.

  In Patent Document 2, a thin film made of an inorganic oxide such as silicon oxide, aluminum oxide, or magnesium oxide is formed on at least one surface of a porous film made of wholly aromatic polyamide or a base material made of nonwoven fabric on the positive electrode side. A formed electrode separator is disclosed. A thin film made of an inorganic oxide is formed by a vacuum deposition method such as sputtering. The separator described in Patent Document 2 has good heat resistance and electrochemical stability (oxidation resistance), but has a problem of low productivity. Further, when the substrate is a non-woven fabric, there is a risk of damage in the vacuum deposition method.

  Patent Document 3 discloses a base material such as a woven fabric or a non-woven fabric made of a polymer or natural fiber, and a separator made of a porous inorganic coating. Inorganic coatings include inorganic particles made of metal Al, Zr, Si, Ti and / or Y oxides, inorganic oxide sols produced by hydrolysis of metal alcoholates, and adhesion aids such as organofunctional silanes. It is comprised from the inorganic binder component which consists of.

  Although the heat resistance of the separator described in Patent Document 3 is good, there is a problem in workability such as peeling of inorganic particles during processing such as battery preparation.

  In Patent Document 4, a fibrous porous substrate such as a nonwoven fabric having a heat resistant temperature of 150 ° C. or higher, filler particles containing boehmite, a resin A having a melting point in the range of 80 to 130 ° C., and an electrolytic solution by heating. A separator for an electrochemical element is disclosed which comprises a porous film containing at least one resin selected from the resin B which absorbs and swells and increases the degree of swelling as the temperature rises. Although the heat resistance is improved as compared with polyolefin and the like, since the resins A and B are both thermoplastic resins, the separator described in Patent Document 4 is a lithium that requires high energy density. It was difficult to say that the separator of the ion secondary battery had sufficient heat resistance.

  Patent Document 5 discloses a separator made of a boehmite free-standing film containing an organic polymer binder and an ion conductive polymer. In order to produce, there existed a problem of requiring a complicated process.

  Patent Document 6 discloses a separator for a non-aqueous electrolyte battery in which an organic metal compound such as an organic silicon compound or an organic aluminum compound is attached to a porous substrate such as a nonwoven fabric containing organic fibers. The separator described in Patent Document 6 is manufactured by impregnating, coating, or spraying a base material with an organometallic compound solution, drying, and heat-curing (sol-gel method), and the base material is made of a metal oxide gel layer. It is covered. In the separator obtained by this production method, the coating layer may be peeled off, and the heat resistance required for a high energy density lithium ion secondary battery may not be achieved.

JP 2000-030686 A JP 2001-038442 A JP-T-2006-504228 JP 2007-157723 A Japanese Patent No. 4426721 International Publication No. 98/032184 Pamphlet

  The first problem to be solved by the present invention is a non-aqueous electrolyte battery that is excellent in heat resistance and dimensional stability, has no peeling of the coating layer during processing such as battery production, and can be manufactured by a simple method and process. Is to provide a separator. The second problem to be solved by the present invention is to provide a lithium ion secondary battery having high safety even in a high temperature environment due to abnormal heat generation.

  As a result of intensive research in order to solve the above problems, the present inventors have found that a woven fabric formed from organic fibers coated with an inorganic oxide gel layer formed from inorganic oxide hydrate particles or In non-aqueous electrolyte battery separators made of non-woven fabric, by making inorganic oxide hydrate particles having an average particle diameter in a specific range, heat resistance, dimensions compared to conventional non-aqueous electrolyte battery separators It has been found that the separator has excellent stability and does not peel off the coating layer during processing such as battery production, and the present invention has been completed based on this finding.

That is, the present invention
1. A non-aqueous electrolyte battery separator comprising a woven or non-woven support formed from organic fibers and a support coating layer containing inorganic oxide hydrate particles, the porosity of the non-aqueous electrolyte separator Is 20 to 80%, the thickness of the support coating layer is 10 to 400 nm, the average diameter of the organic fibers is 1 to 15 μm, and the inorganic oxide hydrate particles satisfy the following (1) A separator for a non-aqueous electrolyte battery.
(1) 3 ≦ d50 ≦ 20 (nm)
(However, d50 represents the particle diameter of 50% by volume cumulatively calculated from the small particle side in the particle size distribution of the inorganic oxide hydrate particles measured by the dynamic light scattering method. However, the particle shape is not spherical. (In this case, the diameter of a sphere corresponding to the same volume is defined as the particle diameter. The unit of d50 is nm.)
2. The inorganic oxide hydrate particles satisfy the following (2): A separator for a non-aqueous electrolyte battery according to 1.
(2) 0 <α ≦ 2.5
(However, α indicates the uniformity of the particle size distribution and is expressed by α = (d90−d10) / d50. In the particle size distribution of the inorganic oxide hydrate particles measured by the dynamic light scattering method, Similarly, d50 and d10 represent a particle diameter of 90% by volume from the small particle side, and d50 and d10 represent a particle diameter of 50% by volume and 10% by volume, respectively. d50 is the same as the above definition.)
3. 1. The inorganic oxide gel layer further contains an organopolysiloxane. Or 2. A separator for a non-aqueous electrolyte battery according to 1.
4). The inorganic oxide hydrate particles are at least one selected from alumina hydrate particles, silica hydrate particles, titania hydrate particles, and zirconia hydrate particles. ~ 3. A separator for a non-aqueous electrolyte battery according to any one of the above.
5. 1. The inorganic oxide hydrate particles are alumina hydrate particles. ~ 4. A separator for a non-aqueous electrolyte battery according to any one of the above.
6). 4. The crystal system of the alumina hydrate particles is (pseudo) boehmite. A separator for a non-aqueous electrolyte battery according to 1.
7). 2. The organopolysiloxane is a polymer obtained from an alkoxysilane having an epoxy group, a vinyl group, an acryloyl group, or a methacryloyl group. A separator for a non-aqueous electrolyte battery according to 1.
8). 2. The organopolysiloxane is a polymer obtained from 3-glycidoxypropyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, or vinyltrimethoxysilane. A separator for a non-aqueous electrolyte battery according to 1.
9. At least one of the organic fibers is polyester, polyolefin, cellulose or cellulose derivative. ~ 8. A separator for a non-aqueous electrolyte battery according to any one of the above.
10. 8. The at least one organic fiber is polyester. A separator for a non-aqueous electrolyte battery according to 1.
11. 1 above. -10. A lithium ion secondary battery comprising the nonaqueous electrolyte battery separator according to any one of the above.
12 10. It is a stacked lithium ion secondary battery. The lithium ion secondary battery described in 1.
13. 10. It is a wound type lithium ion secondary battery. The lithium ion secondary battery described in 1.

  The separator for a non-aqueous electrolyte battery of the present invention is excellent in heat resistance, has good workability, and can be manufactured by a simple method and a short process, and thus has high productivity. The lithium ion secondary battery using the non-aqueous electrolyte battery separator of the present invention has high safety even in a high temperature environment due to abnormal heat generation, and can suppress the weight even when a large number of battery cells are mounted.

[Separator for non-aqueous electrolyte battery]
The separator for a nonaqueous electrolyte battery of the present invention (hereinafter simply referred to as a separator) includes a woven or non-woven (including paper) support formed from organic fibers, and a support containing inorganic oxide hydrate particles. It is a porous sheet comprising a coating layer, and the inorganic oxide hydrate particles are required to satisfy the following (1).

(1) 3 ≦ d50 ≦ 20 (nm)
(However, d50 is the same as above)
When the value of d50 exceeds 20 nm, the adhesion of the inorganic oxide hydrate particles to the support decreases, the inorganic oxide hydrate particles fall off, and the coating layer easily peels off. There is a possibility that workability is lowered and heat resistance is also lowered. On the other hand, inorganic oxide hydrate particles having a d50 value of less than 3 nm are difficult to produce.
The inorganic oxide hydrate particles preferably satisfy the following (1) ′.

(1) '20 ≦ d (F) / d50 ≦ 2000
When d (F) / d50 (d (F) represents the average diameter of the organic fibers) is less than 20, the inorganic oxide hydrate particles fall off or the support coating layer easily peels off. . On the other hand, when d (F) / d50 exceeds 2000, the separator becomes too thick and the energy density of the lithium ion secondary battery used decreases, so 20 ≦ d (F) / d50 ≦ 2000, more preferably It is preferable to use organic fibers and inorganic oxide hydrate particles that satisfy 200 ≦ d (F) / d50 ≦ 1000.

  Furthermore, the inorganic oxide hydrate particles preferably satisfy the following (2).

(2) 0 ≦ α ≦ 2.5
(However, α is the same as above)
If the value of α exceeds 2.5, the adhesion of the inorganic oxide hydrate particles to the support will be reduced, and the inorganic oxide hydrate particles will fall off or the coating layer will be easily peeled off. There is.

Inorganic oxide hydrate is substantially non-conductive, chemically stable to electrolytes, other materials used to make batteries, and electrochemically stable If it is a thing, it will not specifically limit. Alumina hydrate, silica hydrate, titania hydrate, and zirconia hydrate are preferable from the viewpoint of easy availability and economy. Silica hydrate and alumina hydrate are more preferable, and alumina hydrate is particularly preferable. A plurality of inorganic oxide hydrates may be used in combination.
Alumina hydrate includes gypsite, bayerite, boehmite, pseudoboehmite, diaspore, amorphous and the like depending on the crystal system. Either can be used, but boehmite or pseudoboehmite is preferred. Boehmite is a crystal of alumina hydrate represented by the composition formula Al ₂ O ₃ .nH ₂ O (n = 1 to 1.5). Pseudoboehmite refers to a colloidal aggregate of boehmite.

  The shape of the inorganic oxide hydrate particles is not particularly limited, but in order to prevent internal short circuit more effectively, plate-like particles are preferable. In the present invention, a plate-like particle means a particle having a maximum length / minimum length ratio exceeding 2, and a spherical particle means a particle having a maximum length / minimum length ratio of 1 to 2. The plate-like particles include particles having various shapes such as a columnar shape and a fiber shape depending on the ratio (aspect ratio) of the length (major axis) and the minor axis direction length (minor axis) of the flat plate surface. In order to increase the effect of preventing internal short circuit, particles having an aspect ratio of 1 to 50 are preferable, and particles having 1 to 2 are more preferable.

  The support coating layer containing the inorganic oxide hydrate particles preferably further contains an organopolysiloxane. When the organopolysiloxane is contained, the adhesion between the support and the coating layer is improved. The organopolysiloxane is a polymer having a repeating unit of silicon-oxygen bond (Si—O—Si), and a silicon atom is substituted with at least one organic group. Organopolysiloxanes include methylpolysiloxane, dimethylpolysiloxane, methylphenylpolysiloxane, methylhydrogenpolysiloxane, methylstyrene modified silicone, long chain alkyl modified silicone, polyether modified silicone, amino modified silicone, carbinol modified silicone, Examples thereof include epoxy-modified silicone, carboxyl-modified silicone, mercapto-modified silicone, and methacryl-modified silicone.

  As content of organopolysiloxane, the range of 10-90 volume% is preferable with respect to a support body coating layer, More preferably, it is 30-70 volume%.

  The thickness of the support coating layer containing the inorganic oxide hydrate particles is 10 to 400 nm, preferably 20 to 100 nm. When the thickness is less than 10 nm, it is difficult to coat uniformly, and the effect of improving heat resistance is hardly exhibited. On the other hand, when the thickness is larger than 400 nm, the coating layer is easily peeled off.

  The support may be a woven or non-woven fabric formed from organic fibers, and the non-woven fabric may be paper.

  Examples of the organic fiber forming the woven or non-woven fabric used as the support include polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyolefins such as polyethylene and copolymers thereof, polypropylene and copolymers thereof; cellulose, carboxy Examples thereof include cellulose derivatives such as methylcellulose and hydroxypropylcellulose; polyacrylonitrile; polyamide, polyamideimide, polyimide and the like, and two or more kinds of fibers may be included.

  The thickness of the support is 10 to 70 μm, preferably 15 to 50 μm. When the support is too thick, the energy density of the used lithium ion secondary battery is lowered. On the other hand, if it is too thin, the strength of the separator is reduced and workability is reduced.

  The average diameter of the organic fiber forming the support is 1000 to 15000 nm, more preferably 2000 to 10,000 nm. In the present invention, the average diameter of the organic fibers forming the support is randomly determined from a photograph obtained by photographing the surface of a woven or non-woven fabric as a support with a scanning electron microscope (magnification 500 to 10,000 times). It means the average value (n = 10) calculated by selecting the 10 locations and measuring the diameter of the fiber. If the organic fiber forming the support is too thick, the gaps in the separator will increase, increasing the possibility of causing an internal short circuit, and further increasing the thickness of the separator, thus reducing the energy density of the lithium ion secondary battery used. . On the other hand, if it is too thin, the strength of the separator is reduced and workability is reduced.

The thickness of the support described above, and the average diameter of the organic fibers forming the support is preferably 5 to 30 g / m ² as a weight per unit area, further 10 to 25 g / m ² is preferred.

  Moreover, when the separator of this invention consists of a nonwoven fabric support body formed from an organic fiber, you may contain the fibrillated fiber whose fiber diameter is 1 micrometer or less in the nonwoven fabric.

  The porosity of the separator of the present invention is preferably 20 to 80%, more preferably 30 to 70%. When the porosity is less than 20%, the lithium ion permeability is greatly reduced. On the other hand, when the porosity exceeds 80%, the strength of the separator is reduced or internal short circuit is easily caused.

  The manufacturing method of the separator of this invention is demonstrated.

  A coating layer composed of inorganic oxide hydrate particles can be formed on the surface of the organic fiber forming the support by a sol-gel method. That is, a coating layer can be formed by applying an inorganic oxide hydrate sol to a support on a woven or non-woven fabric made of organic fibers having the above-described physical properties (material, average fiber diameter, thickness, etc.) and drying.

  As the woven or non-woven fabric made of organic fibers used for producing the separator of the present invention, commercially available products can be used as long as they have the above-described physical properties. When manufacturing a nonwoven fabric, a general method can be utilized. That is, a non-woven fabric can be produced by forming a fiber web made of organic fibers and bonding, fusing, and entanglement of the fibers in the web. Examples of the method for forming the fiber web include a dry method such as a card method and an air array method, a wet method such as a papermaking method, a spun bond method, and a melt blow method. When it is desired to obtain a separator with an emphasis on the difficulty of pinholes and mechanical strength, a wet method capable of obtaining a homogeneous and dense fiber web is preferred. In the wet method, short fibers having a length of several millimeters are dispersed in water to form a uniform papermaking slurry, and a fiber web is formed using a papermaking machine. Examples of a method for producing a nonwoven fabric from a fiber web include a chemical bond method, a thermal bond method, a hydroentanglement method, and a needle punch method. When trying to obtain a dense nonwoven fabric with high homogeneity, the chemical bond method and the thermal bond method are preferable. The nonwoven fabric made of organic fibers thus obtained is preferably further pressurized by a calender or the like to adjust the thickness or make it uniform.

  The inorganic oxide hydrate sol is an aqueous sol (dispersion) in which alumina hydrate, silica hydrate, titania hydrate, and zirconia hydrate satisfying the above (1) with respect to the average particle size are dispersed. Medium: water, water-water-soluble organic solvent) or organosol (dispersion medium: organic solvent, water content is 10% by mass or less) is preferable, and those satisfying the above (2) are more preferable. In the present invention, the water-soluble organic solvent refers to an organic solvent that can be dissolved in water at a temperature of 20 ° C., alcohols such as methanol, ethanol, propanol, ethylene glycol, and glycerin, ketones such as acetone, acetic acid, and the like. And aprotic polar solvents such as tetrahydrofuran, N, N-dimethylformamide, N, N-dimethylacetamide and N-methyl-2-pyrrolidone. If necessary, the inorganic oxide hydrate sol may contain a dispersion stabilizer such as an acid or an alkali so that the inorganic oxide hydrate particles are stably present in the medium. As long as the above (1) and (2) are satisfied, the inorganic oxide hydrate sol may be purchased commercially or synthesized by a known method.

  As the inorganic oxide hydrate sol, those in which alumina hydrate is dispersed are preferable, and sols in which boehmite or pseudoboehmite is dispersed are particularly preferable. Examples of aqueous sols and organosols in which commercially available alumina hydrate is dispersed include “Aluminum Sol-10A”, “Aluminum Sol-A2”, “Aluminum Sol-10D” (trademark, manufactured by Kawaken Fine Chemical Co., Ltd.), etc. Is mentioned.

  If the inorganic oxide hydrate sol precursor has moderate stability to hydrolysis, such as when trying to coat silica hydrate, it can also be coated by applying and drying the sol precursor-containing liquid. Layers can be formed. The inorganic oxide hydrate sol precursor is a compound that generates an inorganic oxide hydrate by hydrolysis, and is a metal compound having a hydrolyzable group (see Patent Document 6). Examples of the hydrolyzable group include a chlorine atom, an alkoxy group, and an acyloxy group. However, since this method hydrolyzes after being applied to the support, the hydrolysis conditions are limited by the support. Therefore, depending on the inorganic oxide hydrate sol precursor, the above (1) and (2) are satisfied. Inorganic oxide hydrate particles may not be obtained.

  When the above-mentioned organopolysiloxane is contained, it is added so as to be in the range of 10 to 90% by mass, more preferably 30 to 70% by mass with respect to the support coating layer.

  Instead of the organopolysiloxane, an organopolysiloxane precursor (an organosilicon compound that generates an organopolysiloxane by hydrolysis or condensation polymerization) may be used. The organopolysiloxane precursor is an organosilicon compound in which one or more hydrolyzable groups (preferably alkoxy groups or acyloxy groups) are substituted on silicon atoms, and includes methoxytrimethylsilane, dimethyldimethoxysilane, and methyltrimethoxysilane. And alkoxysilanes such as phenyltrimethoxysilane and tetramethoxysilane, acyloxysilanes such as acetoxytrimethylsilane, diacetoxydimethylsilane, and methyltriacetoxysilane, and silane coupling agents. A plurality of organopolysiloxane precursors may be used in combination.

  The silane coupling agent is an organosilicon compound having a hydrolyzable group and a carbon functional group having reactivity and interaction with the organic compound. For example, the general formula (1)

（ただし、式（１）中、Ｒ^１はエポキシ基、エポキシシクロヘキシル基、アクリロイル基、メタクリロイル基、ビニル基、メルカプト基、置換基を有していてもよいアミノ基、水酸基からなる群から選ばれた基、Ｒ^２、Ｒ^３、Ｒ^４は各々独立に、炭素数１〜６の鎖状のアルキル基、フェニル基、アルコキシ基、アシルオキシ基、ハロゲン原子、炭素数１〜６のハロゲノアルキル基からなる群から選ばれた基、Ｘは下記一般式（２）（式（２）中、ｍ＋ｎは０〜６の整数である）で表される２価のメチレン基）
で表される有機ケイ素化合物である。

(In the formula (1), R ¹ is selected from the group consisting of an epoxy group, an epoxycyclohexyl group, an acryloyl group, a methacryloyl group, a vinyl group, a mercapto group, an optionally substituted amino group, and a hydroxyl group. R ² , R ³ and R ⁴ are each independently a chain alkyl group having 1 to 6 carbon atoms, a phenyl group, an alkoxy group, an acyloxy group, a halogen atom, or a halogenoalkyl group having 1 to 6 carbon atoms. X is a divalent methylene group represented by the following general formula (2) (wherein m + n is an integer of 0 to 6):
It is an organosilicon compound represented by.

シランカップリング剤としては、３−グリシドキシプロピルトリメトキシシラン、３−グリシ
ドキシプロピルメチルジメトキシシラン、３−グリシドキシプロピルトリエトキシシラン、３−グリシドキシプロピルメチルジエトキシシラン、２−（３，４−エポキシシクロヘキシル）エチルトリメトキシシラン、３−アクリロキシプロピルトリメトキシシラン、３−メタクリロキシプロピルトリメトキシシラン、３−メタクリロキシプロピルメチルジメトキシシラン、３−メタクリロキシプロピルメチルジエトキシシラン、ビニルトリメトキシシラン、ビニルトリアセトキシシラン、３−メルカプトプロピルトリメトキシシラン、３−アミノプロピルトリメトキシシラン、３−アミノプロピルトリエトキシシラン、３−（２−アミノエチル）アミノプロピルトリメトキシシラン、３−（２−アミノエチル）アミノプロピルメチルジメトキシシラン、Ｎ−フェニル−３−アミノプロピルトリメトキシシラン、３−ヒドロキシプロピルトリメトキシシラン、２−ヒドロキシエチルトリメトキシシラン、３−クロロプロピルトリメトキシシランなどが挙げられる。
シランカップリング剤の反応性官能基としてエポキシ基、ビニル基、アクリロイル基、メタクリロイル基を有するシランカップリング剤がより好ましく、エポキシ基を有するシランカップリング剤が特に好ましい。

Examples of silane coupling agents include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, Vinyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3- (2-aminoethyl) a Nopropyltrimethoxysilane, 3- (2-aminoethyl) aminopropylmethyldimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, 3-hydroxypropyltrimethoxysilane, 2-hydroxyethyltrimethoxysilane, 3- And chloropropyltrimethoxysilane.
A silane coupling agent having an epoxy group, a vinyl group, an acryloyl group or a methacryloyl group as a reactive functional group of the silane coupling agent is more preferable, and a silane coupling agent having an epoxy group is particularly preferable.

  When using an organopolysiloxane precursor, it is preferable to coexist a condensation polymerization catalyst. The content of the condensation polymerization catalyst is preferably in the range of 0.1 to 5.0% by mass, more preferably 0.5 to 3.0% by mass with respect to the organopolysiloxane precursor. As polycondensation catalysts for organopolysiloxane precursors, metal salts of carboxylic acids such as alkyl titanates, tin octylate and dibutyltin dilaurate, dioctyltin dimaleate, N- (2-aminoethyl) ethanolamine, tetraethylpentamine Amino group-containing silane coupling agents such as N-β-aminoethyl-γ-aminopropyltrimethoxysilane, N-β-aminoethyl-γ-aminopropylmethyldimethoxysilane, p-toluenesulfonic acid, Acids such as phthalic acid and hydrochloric acid; aluminum compounds such as aluminum alkoxide and aluminum chelate; alkali catalysts such as potassium hydroxide; titanium compounds such as tetraisopropyl titanate, tetrabutyl titanate and titanium tetraacetylacetonate That.

  In order to improve the adhesion of the coating layer to the support, the support surface may be subjected to corona discharge treatment or plasma discharge treatment.

  Inorganic oxide hydrate and, if necessary, further contain organopolysiloxane so that the thickness of the support coating layer containing inorganic oxide hydrate particles is 10 to 400 nm, preferably 20 to 100 nm. The coating liquid to be applied is applied to the support. When the above-mentioned organopolysiloxane is contained in the support coating layer, a method of applying an inorganic oxide hydrate sol containing organopolysiloxane to the support and drying, applying an organopolysiloxane solution to the support, Method of applying and drying inorganic oxide hydrate sol after drying, Method of applying and drying organopolysiloxane solution after applying and drying inorganic oxide hydrate sol, Supporting organopolysiloxane solution After coating and drying, a coating layer can be formed by a method of coating and drying an inorganic oxide hydrate sol containing organopolysiloxane on a support.

  Various general coating methods can be employed depending on the viscosity of the coating liquid and the desired shape and size of the coating layer. Examples of the coating method include fluency / dipping method, doctor blade coating method, knife coating method, bar coating method, spin coating method, gravure coating method, screen coating method, spraying method by spray, roll coating method and the like. The roll coating method is preferable because of high production efficiency. The conveying speed of the support to be applied may be appropriately adjusted depending on the desired thickness of the coating layer, but is preferably in the range of 0.5 to 50 m / min.

It is dried at a temperature that does not change the quality of the support made of organic fibers used (discoloration, shrinkage, softening, melting, etc.). For example, when the material of the support is polypropylene, the drying temperature is 20 to 130 ° C., and when polyester is 20 to 200 ° C.
[Lithium ion secondary battery]
The lithium ion secondary battery of the present invention is characterized by using the separator for a non-aqueous electrolyte battery of the present invention described above, and known electrodes and electrolytes can be used and manufactured by a known manufacturing method. Is possible.

For the positive electrode constituting the electrode, as the active material, for example, LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , lithium-containing metal oxides such as LiFePO ₄ , What mixed these substances in arbitrary ratios can be used. Moreover, what substituted these transition metal parts with other elements, such as Al, can also be used. N-methyl-2-pyrrolidone together with a conductive aid such as carbon black, a binder such as polyvinylidene fluoride (PVdF) and styrene butadiene rubber (SBR), and a thickener such as carboxymethylcellulose (CMC). A positive electrode is formed by a method of dispersing in an organic solvent such as (NMP) or an aqueous solvent, applying the solution on a metal foil such as aluminum, and drying the solvent.

  As the active material, for example, a graphite material, an amorphous carbon material, a silicon material, lithium metal, a lithium alloy compound, or the like, or a mixture of these materials at an arbitrary ratio can be used for the negative electrode. N-methyl-2-pyrrolidone together with a conductive aid such as carbon black, a binder such as polyvinylidene fluoride (PVdF) and styrene butadiene rubber (SBR), and a thickener such as carboxymethylcellulose (CMC). A negative electrode is formed by a method of dispersing in an organic solvent such as (NMP) or an aqueous solvent, applying the solution on a metal foil such as copper, and drying the solvent.

As the non-aqueous electrolyte, for example, a solution obtained by dissolving an electrolyte such as a lithium salt in a non-aqueous solvent can be used. Nonaqueous solvents include cyclic carbonates that are high dielectric constant solvents such as propylene carbonate (PC) and ethylene carbonate (EC), and chain carbonates that are low viscosity solvents such as diethyl carbonate (DEC) and dimethyl carbonate ( DMC), ethyl methyl carbonate (EMC), or the like may be used alone or in combination of two or more. As the lithium salt used in the electrolyte, inorganic lithium salts such as LiPF ₆ and LiBF ₄ , or organic lithium salts such as LiN (SO ₂ CF ₃ ) ₂ (LiTFSI) and LiCF ₃ SO ₃ can be used, A mixture of two or more of these lithium salts can also be used. Moreover, it is also possible to add various additives, such as a negative electrode protective film formation agent, for example, vinylene carbonate (VC), a flame retardance imparting agent, an overcharge prevention agent, to this electrolyte solution.

  Regardless of the material and shape of the exterior body, for example, a cylindrical can or square can made of metal such as aluminum or stainless steel, or aluminum whose surface is coated with polypropylene, polyethylene, polyethylene terephthalate, etc. Examples thereof include a sheet-type exterior body using a laminate film.

  The lithium ion secondary battery of the present invention includes a stacked lithium ion secondary battery manufactured by alternately stacking positive and negative electrodes via separators, and a spiral (cylindrical type) of positive and negative electrodes via separators. Or a wound lithium ion secondary battery manufactured by winding into a flat shape (square shape).

  Next, examples will be shown and described in more detail, but the present invention is not limited to these examples.

  Each value in the examples was determined by the following method.

[Particle size / size distribution]
It was measured by a dynamic light scattering type particle size / particle size distribution measuring device (trademark “Nanotrack UPA-EX150”, manufactured by Nikkiso Co., Ltd.). When the particle shape is not spherical, it is converted to a sphere diameter corresponding to the same volume.

[Average fiber diameter]
Ten locations were selected at random from a photograph obtained by photographing the surface of a woven or nonwoven fabric as a support with a scanning electron microscope (JSM-5500LV, manufactured by JEOL Ltd.) (magnification 500 to 10,000 times). The diameter of the fiber was measured, and the average value of all the fiber diameters (n = 10) was obtained to obtain the average diameter of the fibers.

[Porosity]
The pore size distribution (cumulative pore volume) was measured with a mercury porosimeter (PoreMaster 60-GT, manufactured by Quantachrome Instruments Co.), and the porosity of the separator was calculated according to the following equation.

Porosity (%) = pore volume P (cm ³ ) / bulk volume of sample (cm ³ ) × 100
Pore volume P (cm ³ ) = cumulative pore volume (cm ³ g ⁻¹ ) × sample weight (g)
Bulk volume of sample (cm ³ ) = total cell volume (cm ³ ) −cell internal volume excluding sample (cm ³ )

[Tensile strength, elongation at break]
The separator was punched with a JIS K 7127 test piece type 2 dumbbell to prepare a test piece (10 mm × 150 mm × 0.03 mm). The prepared test piece is set on a Tensilon universal testing machine (RTC-1310A type, manufactured by A & D Co., Ltd.), and the tensile strength and elongation at break are measured under the conditions of a pulling speed of 50 mm / min and a distance between grips of 100 mm. It was measured.

dx: Particle size of cumulative volume x volume% calculated from the small particle side in the particle size distribution of the inorganic oxide hydrate particles measured by the dynamic light scattering method α: (d90-d10) / d50

〔Heat-resistant〕
A soldering iron with a tip of 0.3 mm was heated to various temperatures, and the size of the hole that was opened when the soldering iron was brought into contact with the separator for 15 seconds was measured.

Separator 1
Aqueous boehmite sol (Trademark “Aluminum sol-10A”, boehmite content: 10% by mass, manufactured by Kawaken Fine Chemical Co., Ltd., d50: 8 nm, α: 0.82) is diluted with ethanol so that the concentration becomes 1/2 Thus, a coating solution was prepared. This coating solution was applied to a non-woven fabric made of polyester (average diameter: 4 μm, basis weight: 14 g / m ² , 1 × 100 m, Nippon Vilene Co., Ltd.) by a roll coating method. The conveyance speed of the nonwoven fabric was 6 m / min. After application, a separator for a nonaqueous electrolyte battery was produced by drying with hot air at 100 ° C.

  The obtained separator had a porosity: 42.9%, a tensile strength: 10.4 MPa, and an elongation at break: 28%. In addition, a peel test was performed using an industrial tape (registered trademark “Cello Tape”, product number: 405, Nichiban Co., Ltd.). The test was repeated 10 times, but no peeling was observed.

Separator 2
An aqueous boehmite sol was used as an organopolysiloxane precursor-containing aqueous boehmite sol (Trademark “Aluminosol CSA-110AD” boehmite content: 6.3% by mass, organopolysiloxane precursor: 3-glycidoxypropyltrimethoxysilane 6% by mass, A separator for a non-aqueous electrolyte battery was obtained in the same manner as in Example 1 except that d50: 8 nm, α: 0.82, manufactured by Kawaken Fine Chemical Co., Ltd.). The resulting test piece from the separator (about 1 m ²⁾ four points (coating start portion, the intermediate portion × 2, coating end portion) by measuring the mass was collected, was calculated coating mass per unit area, It was 1.629, 1.610, 1.740 g, 1.68 g / m ² .

  The separator obtained had a porosity of 33.3%, a tensile strength of 33.7 MPa, and an elongation at break of 27%. A tape peeling test was conducted in the same manner as in Example 1, but no peeling was observed.

  A polyester non-woven fabric similar to that of Example 1 was prepared by subjecting an aqueous boehmite sol (trademark “aluminum sol-A2” boehmite content: 10% by mass, manufactured by Kawaken Fine Chemical Co., Ltd., d50: 9 nm, α: 0.69) to a roll coating method It was applied to. The conveyance speed of the nonwoven fabric was 6 m / min. After application, a separator for a nonaqueous electrolyte battery was produced by drying with hot air at 100 ° C.

Non-aqueous electrolyte battery in the same manner as in Example 1 except that the polyester non-woven fabric was changed to an average diameter of 4 μm, basis weight: 19.2 g / m ² , 1 × 100 m, manufactured by Nippon Kogyo Paper Industries Co., Ltd. A separator was obtained.

For non-aqueous electrolyte batteries in the same manner as in Example 2 except that the polyester non-woven fabric was changed to an average diameter of 4 μm, a basis weight of 19.2 g / m ² , 1 × 100 m, manufactured by Nippon Kogyo Paper Industries Co., Ltd. A separator was obtained.

  A polyester non-woven fabric (both boehmite content: 6.3% by mass, organopolysiloxane precursor: 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane) by roll coating method with an organopolysiloxane precursor-containing aqueous boehmite sol The same as in Example 1 was applied. The conveyance speed of the nonwoven fabric was 6 m / min. After application, a separator for a nonaqueous electrolyte battery was produced by drying with hot air at 100 ° C.

  A separator for a nonaqueous electrolyte battery was produced in the same manner as in Example 6 except that the organopolysiloxane precursor contained in the organopolysiloxane precursor-containing aqueous boehmite sol was changed to vinyltrimethoxysilane.

  A separator for a nonaqueous electrolyte battery was produced in the same manner as in Example 3 except that the aqueous boehmite sol was changed to zirconia sol (zirconia content: 10% by mass, d50: 17.2 nm, α: 2.3).

Comparative Example 1

Polyester nonwoven fabric used in Example 1 (average diameter: 4 μm, basis weight: 14 g / m ² , 1 × 100 m, Nippon Vilene Co., Ltd.) tape peel test, porosity, tensile strength, elongation at break, heat resistance It was measured.

Comparative Example 2

Tape peeling test, porosity, tensile strength, elongation at break of polyester nonwoven fabric (average diameter: 4 μm, basis weight: 19.2 g / m ² , 1 × 100 m, Nippon Kogyo Paper Industries Co., Ltd.) used in Example 4 The heat resistance was measured.

Comparative Example 3

  A separator for a non-aqueous electrolyte battery is obtained in the same manner as in Example 3 except that the aqueous boehmite sol is changed to an aqueous boehmite sol having a boehmite content of 10% by mass, d50: 24.8 nm, and α: 3.12. It was.

Comparative Example 4

  A separator for a nonaqueous electrolyte battery was obtained in the same manner as in Example 3 except that the aqueous boehmite sol was changed to an aqueous boehmite sol having a boehmite content of 10 mass%, d50: 102 nm, and α: 3.74.

Comparative Example 5

  A separator for a nonaqueous electrolyte battery was produced in the same manner as in Example 3 except that the aqueous boehmite sol was changed to zirconia sol (zirconia content: 20% by mass, d50: 87.2 nm, α: 0.82).

  Table 1 summarizes the results of the tape peeling test, porosity, tensile strength, elongation at break, and heat resistance of Examples and Comparative Examples.

実施例で得られたセパレータを使用して、以下に従って、リチウムイオン二次電池を作製した。

Using the separator obtained in the example, a lithium ion secondary battery was produced according to the following.

[Production of positive electrode]
LiNi _1/3 Mn _1/3 Co _1/3 O ₂ (positive electrode active material), polyvinylidene fluoride (binder), carbon black (conducting aid) (88/6/6, mass%) with N-methyl A positive electrode mixture paste was prepared by uniformly dispersing in -2-pyrrolidone. This paste is applied to both sides of an aluminum foil (positive electrode current collector) having a thickness of 15 μm, and after drying the solvent, the paste is pressed to a constant density and adjusted to a total thickness of 66 μm. The positive electrode was produced by cutting to length (length 129 mm × width 65.5 mm).

(Production of negative electrode)
Graphite (negative electrode active material) and polyvinylidene fluoride (binder) (90/10, mass%) were uniformly dispersed in N-methyl-2-pyrrolidone to prepare a negative electrode mixture paste. This paste was applied to both sides of a 10 μm thick copper foil (negative electrode current collector), dried after the solvent was pressed to a constant density, adjusted to a total thickness of 89 μm, The negative electrode was produced by cutting into a size (length 138 mm × width 70.0 mm).

[Electrolyte]
A solution obtained by dissolving lithium hexafluorophosphate in a mixed solvent of propylene carbonate / ethylene carbonate / diethyl carbonate (2/2/6, volume ratio) to 1 mol / L was used as an electrolytic solution.

[Exterior body]
Two aluminum laminate films with polypropylene resin as the inner layer and polyethylene resin as the outer layer and aluminum foil as the intermediate layer are cut out to a predetermined size, and one of them is pressed to form a concave portion of the size of the laminate, and these are stacked It was set as the exterior body by uniting.

[Lithium ion secondary battery]
The separator produced in the above-described example was folded in a Σ shape, and the negative electrode and the positive electrode produced in the above were alternately inserted into a laminate, and a current extraction tab was ultrasonically welded thereto. The laminated body with tabs was sandwiched between two aluminum laminate film exterior bodies, and the outer periphery was heat-welded leaving one side serving as an electrolyte injection port. An appropriate amount of the above electrolyte solution was injected from the electrolyte solution inlet, vacuum degassed and sufficiently impregnated, and then the inlet was thermally welded to produce a lithium ion secondary battery.

  Using the produced lithium ion secondary battery, a nail penetration test and an overcharge test were performed according to the following.

[Charging method]
In a state where the prepared lithium ion secondary battery is uniformly pressed in a plane direction with a constant force, a constant current charge at 0.2 C (0.4 A) is performed with 4.2 V as an upper limit voltage, and further, 4. After reaching 2V, constant voltage charging was performed for 12 hours.

[Nail penetration test] Test A
The lithium ion secondary battery was fully charged by the above charging method. A nail with a diameter of 5 mm was slowly and vertically passed through the center of the cell, and kept as it was, and the presence or absence of smoke / ignition, cell surface temperature, and changes in voltage were observed.

[Overcharge test] Test B
The lithium ion secondary battery was fully charged by the above charging method. Furthermore, constant current charging at 3C (11.7 A) was performed up to 12 V, and held by constant voltage charging for 10 minutes or more after reaching 12 V, and the presence or absence of smoke / ignition, cell surface temperature, and change in voltage were observed.

  The results of the nail penetration test and overcharge test are summarized in Table 2.

  The separator for a non-aqueous electrolyte battery of the present invention has excellent heat resistance, good workability, and high productivity. Therefore, a lithium ion that requires a large capacity and high energy density in which a large number of battery cells are mounted. It is useful for a secondary battery and an electric vehicle (HEV, EV) on which it is mounted.

Claims (13)

A non-aqueous electrolyte battery separator comprising a woven or non-woven support formed from organic fibers and a support coating layer containing inorganic oxide hydrate particles, the porosity of the non-aqueous electrolyte separator Is 20 to 80%, the thickness of the support coating layer is 10 to 400 nm, the average diameter of the organic fibers is 1 to 15 μm, and the inorganic oxide hydrate particles satisfy the following (1) A separator for a non-aqueous electrolyte battery.
(1) 3 ≦ d50 ≦ 20 (nm)
(However, d50 represents the particle diameter of 50% by volume cumulatively calculated from the small particle side in the particle size distribution of the inorganic oxide hydrate particles measured by the dynamic light scattering method. However, the particle shape is not spherical. (In this case, the diameter of a sphere corresponding to the same volume is defined as the particle diameter. The unit of d50 is nm.)
The non-aqueous electrolyte battery separator according to claim 1, wherein the inorganic oxide hydrate particles satisfy the following (2).
(2) 0 ≦ α ≦ 2.5
(However, α indicates the uniformity of the particle size distribution and is expressed by α = (d90−d10) / d50. In the particle size distribution of the inorganic oxide hydrate particles measured by the dynamic light scattering method, Similarly, d50 and d10 represent a particle diameter of 90% by volume from the small particle side, and d50 and d10 represent a particle diameter of 50% by volume and 10% by volume, respectively. d50 is the same as the above definition.) Furthermore, organopolysiloxane is contained, The separator for nonaqueous electrolyte batteries of Claim 1 or 2 characterized by the above-mentioned. The inorganic oxide hydrate particles are at least one selected from alumina hydrate particles, silica hydrate particles, titania hydrate particles, and zirconia hydrate particles. The separator for nonaqueous electrolyte batteries in any one. The non-aqueous electrolyte battery separator according to claim 1, wherein the inorganic oxide hydrate particles are alumina hydrate particles. The separator for a non-aqueous electrolyte battery according to claim 5, wherein the crystal system of the alumina hydrate particles is (pseudo) boehmite. The separator for a non-aqueous electrolyte battery according to claim 3, wherein the organopolysiloxane is a polymer obtained from an alkoxysilane having an epoxy group, a vinyl group, an acryloyl group, or a methacryloyl group. The organopolysiloxane is a polymer obtained from 3-glycidoxypropyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, or vinyltrimethoxysilane. The separator for nonaqueous electrolyte batteries as described. The separator for a nonaqueous electrolyte battery according to any one of claims 1 to 8, wherein at least one of the organic fibers is polyester, polyolefin, cellulose, or a cellulose derivative. The separator for a non-aqueous electrolyte battery according to claim 9, wherein at least one of the organic fibers is polyester. A lithium ion secondary battery using the non-aqueous electrolyte battery separator according to claim 1. The lithium ion secondary battery according to claim 11, wherein the lithium ion secondary battery is a stacked lithium ion secondary battery. The lithium ion secondary battery according to claim 11, wherein the lithium ion secondary battery is a wound type lithium ion secondary battery.